Low normal TSH levels are associated with low bone mineral density in healthy postmenopausal women

Postmenopausal women with higher TSH values within the normal range present improved handgrip strength: a pilot study

OBJECTIVE

To evaluate the possible association between thyroid function within the euthyroid range and musculoskeletal parameters as well as body composition in a sample of postmenopausal women.

METHODS

This cross-sectional study included 96 postmenopausal women with serum thyroid-stimulating hormone (TSH) within the normal laboratory reference range. Fasting venous blood samples were obtained for biochemical/hormonal assessment. Bone status and body composition were measured using Dual Energy X-ray absorptiometry (DXA). Physical activity was quantified using the International Physical Activity Questionnaire (IPAQ) index.

RESULTS

Serum TSH correlated with handgrip strength (HGS, r-coefficient = 0.233, p = .025), and total body bone mineral density (BMD) T-score values (r-coefficient = 0.321, p = .003). HGS measures were associated with BMD (r-coefficient = 0.415, p < .001), with bone mineral content (BMC, r-coefficient = 0.427, p < .001), and lean mass (r-coefficient = 0.326, p = .003). Women with low muscle strength, defined as HGS < 16 kg, had lower TSH levels than women with normal muscle strength (low vs. normal muscle strength, ANCOVA 1.13 ± 0.49 mU/L vs. 1.60 ± 0.83 mU/L, p = 0.024) independently of age, BMD, percentage of body fat or absolute lean mass. Multivariable linear regression analysis showed that HGS values were associated with TSH measurements (β-coefficient = 0.246, p = .014) and BMD T-score values (β-coefficient = 0.306, p = .002). All models were adjusted for age, body mass index (BMI), vitamin D, low-density lipoprotein cholesterol, current smoking, physical activity, and homeostasis model assessment of insulin resistance.

CONCLUSIONS

In this sample of postmenopausal women, lower serum TSH values, within normal range, were associated with lower muscle strength compared to higher normal TSH values. Further research is needed to elucidate the significance of our preliminary findings.

Association of serum thyroid-stimulating hormone and bone mineral density in Chinese adults with normal thyroid function

PURPOSE

This study aims to investigate the association of serum TSH with BMD in Chinese adults with normal thyroid function.

METHODS

These participants were divided into tertiles based on serum TSH levels. Linear regression model and multinomial logistic regression models were used to analyze the associations of continuous BMD and categorical BMD with serum TSH, respectively.

RESULTS

In women younger than 60 years, BMD decreased with the increase of TSH at normal level, while in women older than 60 years, BMD increased with the increase of TSH at normal level; besides, the BMD of women younger than 60 years old was significantly higher than that of women over 60 years old (156.05 ± 39.34 mg/cm3 vs. 86.95 ± 29.51 mg/cm3, P < 0.001). Linear regression results showed negative associations of BMD and normal TSH level in women with age younger than 60 years (β=-4.34, P < 0.001), but this inverse trend was observed in women over 60 years old (β = 2.04, P = 0.041). Both in men younger than 60 years and over 60 years old, BMD decreased with the increase of TSH at normal levels; besides, the BMD of men younger than 60 years was significantly higher than those over 60 years old (143.08 ± 32.76 mg/cm3 vs. 108.13 ± 31.99 mg/cm3, P < 0.001).

CONCLUSIONS

The results demonstrated an opposite trend in BMD at normal TSH levels in younger and elder females, that is, in females younger than 60 years, BMD decreased with the increase of TSH, which indicated that TSH might play a different role in younger and elder females. However, this trend was not significant in males.

Neuroendocrinology of bone

The past decade has witnessed significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone in primary and secondary osteoporosis. Recent breakthroughs have primarily emerged from identifying disease-causing mutations and phenocopying human bone disease in rodents. Notably, using genetically-modified rodent models, disrupting the reciprocal relationship with tropic pituitary hormone and effector hormones, we have learned that pituitary hormones have independent roles in skeletal physiology, beyond their effects exerted through target endocrine glands. The rise of follicle-stimulating hormone (FSH) in the late perimenopause may account, at least in part, for the rapid bone loss when estrogen is normal, while low thyroid-stimulating hormone (TSH) levels may contribute to the bone loss in thyrotoxicosis. Admittedly speculative, suppressed levels of adrenocorticotropic hormone (ACTH) may directly exacerbate bone loss in the setting of glucocorticoid-induced osteoporosis. Furthermore, beyond their established roles in reproduction and lactation, oxytocin and prolactin may affect intergenerational calcium transfer and therefore fetal skeletal mineralization, whereas elevated vasopressin levels in chronic hyponatremic states may increase the risk of bone loss.. Here, we discuss the interaction of each pituitary hormone in relation to its role in bone physiology and pathophysiology.

The impact of thyroid function on total spine bone mineral density in postmenopausal women

PURPOSE

Osteoporosis has been a widespread concern for older women, especially postmenopausal women. Thyroid function is crucial for bone metabolism. However, the relationship between thyroid function variation within thyroxine reference range and bone mineral density (BMD) remains ambiguous. The objective of this study was to evaluate the effect of subclinical hypothyroidism or hyperthyroidism on total spinal BMD in postmenopausal women.

METHODS

Based on data from the National Health and Nutrition Examination Survey (NHANES) 2007-2010, multivariable weighted logistic regression was used to evaluate the relationships between total spine BMD and TSH among postmenopausal women aged ≥50.

RESULTS

After accounting for a number of variables, this study discovered that the middle TSH tertile was associated with a decreased probability of osteoporosis. Additionally, the subgroup analysis revealed that postmenopausal women over the age of 65 or people with an overweight BMI had a clearer relationship between total spine BMD and TSH.

CONCLUSION

The total spinal BMD had a positive relationship with thyroid stimulating hormone in postmenopausal women, and that appropriate TSH level (1.38-2.32 mIU/L) was accompanied by higher total spinal BMD.

High-normal free thyroxine level is related with decreased bone mineral density in nonobese male patients with type 2 diabetes over 50 years old

Background

The prevalence of 'low bone mineral density (BMD)' in Type 2 diabetes (T2DM), especially stratified by body mass index, is seldom reported. The relation of the euthyroid range and low BMD in T2DM remains to be further elucidated.

Objectives

We aim to investigate the thyroid hormones' impact on BMD among euthyroid patients with T2DM.

Design and methods

A total of 1452 hospitalized T2DM patients with normal thyroid function (43.6% males aged over 50 and 56.4% postmenopausal females) were enrolled in this cross-sectional study. BMD was measured at lumbar spine by GE lunar dual-energy X-ray absorptiometry system, and 'low BMD' was defined as T-score <-1.0 SD. The prevalence of 'low BMD' was compared between obese and nonobese (body mass index < 25 kg/m2) groups for both sexes, and the relation of low BMD and free T4 quartiles was explored by multiple logistic regression.

Results

The general prevalence of 'low BMD' was 12.3% for male patients aged over 50 (15.5% in the nonobese group and 8.0% in the obese group) and 49.8% for postmenopausal females (56.7% in the nonobese group and 48.9% in the obese group). After adjustment in multiple linear regression, free T4 level remained significantly related to decreased BMD in nonobese male subgroup. Multiple logistic regression revealed that BMD of the highest free T4 quartile (1.12-1.48 ng/dL) decreased significantly than other three quartiles after adjusting for confounding factors including age, body mass index, serum calcium and creatinine level, fasting glucose, alkaline phosphatase, glycosylated hemoglobin, total cholesterol, and smoking history (OR = 2.724, 95% CI = 1.085-6.840, p = 0.033). No significant relation was found in obese male or postmenopausal female groups.

Conclusion

High-normal free T4 is a potential independent risk factor for 'low BMD' in nonobese male T2DM patients aged over 50. Close attention should be paid to thyroid function profile, even within normal range, in nonobese men with underlying higher fracture risks on diabetes status.

A systematic review of the relationship between normal range of serum thyroid-stimulating hormone and bone mineral density in the postmenopausal women

OBJECTIVE

The aim of this study was adopts meta-analysis in evaluating the correlation between TSH and BMD, as well as osteoporosis in the postmenopausal women with normal thyroid function.

METHODS

Six databases were searched for articles concerning correlation between TSH and BMD in postmenopausal women. The retrieval time was set from the date of database establishment to November 30, 2020. Revman5.3 and Stata12.0 software were used for meta-analysis.

RESULTS

A total of 19 articles were incorporated. The Summary Fisher' Z of the correlation between TSH and BMD was 0.16, 95% CI (0.00, 0.32), and the correlation coefficient of Summary Fisher' Z conversion was 0.158. Study on the relationship between TSH and osteoporosis based on OR demonstrated that the combined OR was 1.76, 95% CI (1.27, 2.45), P < 0.05. The subgroup analyzing results displayed that the risk of osteoporosis of the subjects from community with low TSH was 1.89, 95% CI (1.43, 2.49). The risk of osteoporosis for subjects with low TSH and from hospitals was 1.36, 95% CI (0.46, 3.99); 1.84 for subjects with low TSH and anti-osteoporosis drugs, 95% CI (1.05, 3.22); and 1.74 for those with low TSH but not taking anti-osteoporosis drugs, 95% CI (1.08, 2.82). The dose-response relationship showed that the risk of osteoporosis tended to decrease when TSH was more than 2.5mIu/L.

CONCLUSION

The serum TSH is positively related with BMD in postmenopausal women, and high TSH (> 2.5 mIu/L) within the normal range is possibly helpful to decrease the risk of osteoporosis in postmenopausal women.

Age-related variation in thyroid function - a narrative review highlighting important implications for research and clinical practice

BACKGROUND

Thyroid hormones are key determinants of health and well-being. Normal thyroid function is defined according to the standard 95% confidence interval of the disease-free population. Such standard laboratory reference intervals are widely applied in research and clinical practice, irrespective of age. However, thyroid hormones vary with age and current reference intervals may not be appropriate across all age groups. In this review, we summarize the recent literature on age-related variation in thyroid function and discuss important implications of such variation for research and clinical practice.

MAIN TEXT

There is now substantial evidence that normal thyroid status changes with age throughout the course of life. Thyroid stimulating hormone (TSH) concentrations are higher at the extremes of life and show a U-shaped longitudinal trend in iodine sufficient Caucasian populations. Free triiodothyronine (FT3) levels fall with age and appear to play a role in pubertal development, during which it shows a strong relationship with fat mass. Furthermore, the aging process exerts differential effects on the health consequences of thyroid hormone variations. Older individuals with declining thyroid function appear to have survival advantages compared to individuals with normal or high-normal thyroid function. In contrast younger or middle-aged individuals with low-normal thyroid function suffer an increased risk of adverse cardiovascular and metabolic outcomes while those with high-normal function have adverse bone outcomes including osteoporosis and fractures.

CONCLUSION

Thyroid hormone reference intervals have differential effects across age groups. Current reference ranges could potentially lead to inappropriate treatment in older individuals but on the other hand could result in missed opportunities for risk factor modification in the younger and middle-aged groups. Further studies are now needed to determine the validity of age-appropriate reference intervals and to understand the impact of thyroid hormone variations in younger individuals.

Bone circuitry and interorgan skeletal crosstalk

The past decade has seen significant advances in our understanding of skeletal homeostasis and the mechanisms that mediate the loss of bone integrity in disease. Recent breakthroughs have arisen mainly from identifying disease-causing mutations and modeling human bone disease in rodents, in essence, highlighting the integrative nature of skeletal physiology. It has become increasingly clear that bone cells, osteoblasts, osteoclasts, and osteocytes, communicate and regulate the fate of each other through RANK/RANKL/OPG, liver X receptors (LXRs), EphirinB2-EphB4 signaling, sphingolipids, and other membrane-associated proteins, such as semaphorins. Mounting evidence also showed that critical developmental pathways, namely, bone morphogenetic protein (BMP), NOTCH, and WNT, interact each other and play an important role in postnatal bone remodeling. The skeleton communicates not only with closely situated organs, such as bone marrow, muscle, and fat, but also with remote vital organs, such as the kidney, liver, and brain. The metabolic effect of bone-derived osteocalcin highlights a possible role of skeleton in energy homeostasis. Furthermore, studies using genetically modified rodent models disrupting the reciprocal relationship with tropic pituitary hormone and effector hormone have unraveled an independent role of pituitary hormone in skeletal remodeling beyond the role of regulating target endocrine glands. The cytokine-mediated skeletal actions and the evidence of local production of certain pituitary hormones by bone marrow-derived cells displays a unique endocrine-immune-skeletal connection. Here, we discuss recently elucidated mechanisms controlling the remodeling of bone, communication of bone cells with cells of other lineages, crosstalk between bone and vital organs, as well as opportunities for treating diseases of the skeleton.

Approach to the Patient With a Suppressed TSH

Subclinical hyperthyroidism (SCH) is a laboratory diagnosis defined by a serum thyrotropin (TSH) concentration below the reference range (< 0.4 mU/L in most assays), and a free thyroxine (FT4) and 3,5,3'-triiodothyronine levels (FT3) in the reference range. Many patients diagnosed with SCH will be clinically euthyroid while others may present with manifestations characteristic of thyroid hormone excess, such as tachycardia, tremor, intolerance to heat, bone density loss, or weight loss. In addition to the laboratory abnormalities, patient factors such as age, symptoms, and underlying heart and bone disease are used to stratify patients for the risk of adverse outcomes and determine the appropriate treatment. Evaluation should include repeat thyroid function tests to document persistent TSH suppression, investigation of the underlying cause, as well as evaluation of the patient's risk of adverse outcomes in the setting of a subnormal TSH. Persistent SCH has been associated with an increased risk of a range of adverse events, including cardiovascular events such as atrial fibrillation and heart failure, bone loss and fracture, and in some studies, cognitive decline. Despite the consistent association of these adverse events with SCH, prospective studies showing improved outcomes with treatment remain limited. Management options include observation without active therapy, radioactive iodine ablation of the thyroid, antithyroid medication, thyroid surgery, or radiofrequency ablation, as appropriate for the patient and clinical setting. The choice of therapy should be guided by the underlying etiology of disease, patient factors, and the risks and benefits of each treatment option.

Independent Skeletal Actions of Pituitary Hormones

Over the past years, pituitary hormones and their receptors have been shown to have non-traditional actions that allow them to bypass the hypothalamus-pituitary-effector glands axis. Bone cells-osteoblasts and osteoclasts-express receptors for growth hormone, follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin, oxytocin, and vasopressin. Independent skeletal actions of pituitary hormones on bone have been studied using genetically modified mice with haploinsufficiency and by activating or inactivating the receptors pharmacologically, without altering systemic effector hormone levels. On another front, the discovery of a TSH variant (TSH-βv) in immune cells in the bone marrow and skeletal action of FSHβ through tumor necrosis factor α provides new insights underscoring the integrated physiology of bone-immune-endocrine axis. Here we discuss the interaction of each pituitary hormone with bone and the potential it holds in understanding bone physiology and as a therapeutic target.

Thyroid Hormones Are Not Associated with Plasma Osteocalcin Levels in Adult Population with Normal Thyroid Function

Thyroid hormones (THs) play an indispensable role in skeletal development and bone remodeling. Some studies have reported associations of THs with serum osteocalcin (OC) levels, but the results are quite inconsistent and the molecular mechanism of their simultaneous or interdependent activity on bone is almost unknown. Therefore, the aim of this study was to determine the possible associations of plasma THs with plasma OC levels and the possible mediating effect of OC on the relationship between THs and bone mineral density (BMD). For this purpose, out of the initial 1981 participants, we selected healthy euthyroid participants controlled for available confounding factors that can affect thyroid function and bone metabolism (N = 694). Given our results, we could not confirm any associations of THs with plasma OC levels nor the mediating effect of OC on the relationship between THs and BMD in euthyroid population. In the group of women controlled for menopause status (N = 396), we found a significant negative association of body mass index (BMI) with OC levels (β = −0.14, p = 0.03). We also found a negative association of free triiodothyronine (fT3) (β = −0.01, p = 0.02) and age (β = −0.003, p < 0.001) with BMD, and a positive association of BMI (β = 0.004, p < 0.001) and male gender (β = 0.1, p < 0.001) with BMD. In addition, we found significantly higher plasma OC levels and lower values of BMD in postmenopausal euthyroid women compared with premenopausal euthyroid women. In our opinion, the results of previous studies suggesting an association between circulating THs and serum OC levels may be influenced by an inconsistent selection of participants and the influence of confounding factors.

Thyrotropin, Hyperthyroidism, and Bone Mass

Thyrotropin (TSH), traditionally seen as a pituitary hormone that regulates thyroid glands, has additional roles in physiology including skeletal remodeling. Population-based observations in people with euthyroidism or subclinical hyperthyroidism indicated a negative association between bone mass and low-normal TSH. The findings of correlative studies were supported by small intervention trials using recombinant human TSH (rhTSH) injection, and genetic and case-based evidence. Genetically modified mouse models, which disrupt the reciprocal relationship between TSH and thyroid hormone, have allowed us to examine an independent role of TSH. Since the first description of osteoporotic phenotype in haploinsufficient Tshr +/- mice with normal thyroid hormone levels, the antiosteoclastic effect of TSH has been documented in both in vitro and in vivo studies. Further studies showed that increased osteoclastogenesis in Tshr-deficient mice was mediated by tumor necrosis factor α. Low TSH not only increased osteoclastogenesis, but also decreased osteoblastogenesis in bone marrow-derived primary osteoblast cultures. However, later in vivo studies using small and intermittent doses of rhTSH showed a proanabolic effect, which suggests that its action might be dose and frequency dependent. TSHR was shown to interact with insulin-like growth factor 1 receptor, and vascular endothelial growth factor and Wnt pathway might play a role in TSH's effect on osteoblasts. The expression and direct skeletal effect of a biologically active splice variant of the TSHβ subunit (TSHβv) in bone marrow-derived macrophage and other immune cells suggest a local skeletal effect of TSHR. Further studies of how locally secreted TSHβv and systemic TSHβ interact in skeletal remodeling through the endocrine, immune, and skeletal systems will help us better understand the hyperthyroidism-induced bone disease.

Trabecular bone score in women with differentiated thyroid cancer on long-term TSH-suppressive therapy

INTRODUCTION

Thyrotropin stimulating hormone (TSH) suppression in patients with differentiated thyroid cancer (DTC) aims to decrease the growth and proliferation of thyroid cancer cells. However, the effect of TSH-suppressive therapy on bone microarchitecture remains undefined.

METHODS

Cross-sectional study including 43 women with DTC undergoing TSH-suppressive therapy (sTSH) compared to 20 women also on levothyroxine (LT4) therapy but with TSH in the low-normal range (nTSH) since the thyroid surgery. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA), and trabecular bone score (TBS) was evaluated using the TBS iNsigth software. Fracture risk assessed by FRAX, with and without TBS, was calculated. The relationship between suppressive therapy-related parameters and bone parameters was investigated.

RESULTS

The TBS mean values were not significantly different in the sTSH and nTSH groups (1.273 ± 0.12 vs 1.307 ± 0.14, p = 0.7197). In both groups, postmenopausal women had degraded microarchitecture (TBS 1.216 ± 0.11 vs 1.213 ± 0.09, p = 0.9333), while premenopausal women had normal microarchitecture (1.328 ± 0.11 vs 1.401 ± 0.12, p = 0.195). The percentage of all postmenopausal women with degraded TBS was 54.7%, while the percentage of osteoporosis diagnoses was 16.1%. The TBS-adjusted FRAX-probability of fracture was similar in sTSH and nTSH groups. Body mass index (BMI) and menopausal status were the only variables associated with TBS and BMD.

CONCLUSION

Trabecular microarchitecture assessed by TBS was similar between women on long-term suppressive therapy in DTC and those on LT4 replacement therapy aiming at a TSH level within the low-normal reference range. Low TBS values were observed in postmenopausal women of both groups, suggesting that not only suppressed TSH levels but also a low-normal TSH is associated with deteriorated bone microarchitecture in postmenopausal women following total thyroidectomy.

Low Bone Mineral Density at Initial Diagnosis in Children and Adolescents with Graves' Disease

Previous studies have reported reduced bone mineral density (BMD) in patients with hyperthyroidism. We assessed the association of BMD in children and adolescents with Graves' disease (GD) after correcting for potential confounders affecting BMD such as age, sex, and pubertal status. Forty-four children and adolescents with GD and 172 age- and sex-matched healthy controls were enrolled in this study. We analyzed auxological features, BMD, and levels of thyroid hormone, thyroid-stimulating hormone, and thyroid autoantibodies. We measured BMD by dual-energy X-ray absorptiometry at the time of diagnosis in all patients. The mean age of all patients with GD (9 boys and 32 girls) was 12.1 ± 2.2 years (range, 7.0-16.0). Their initial mean free T4 and thyroid-stimulating hormone levels were 3.51 ± 1.56 ng/dL and 0.04 ± 0.03 IU/L, respectively. The mean BMD Z-scores of the lumbar spine (LS), femoral neck, and total body less head of patients with GD were significantly lower than those of control subjects. Eleven patients (26.8%) had low bone density (LS BMD Z-scores < -2.0). To identify correlations of patient characteristics with BMD Z-scores at each site, alkaline phosphatase had a significant negative correlation with BMD Z-scores at LS and femoral neck, but not total body less head (r = -0.441; p = 0.004 and r = -0.351; p = 0.025, respectively). Children and adolescents with newly diagnosed GD had lower bone mass than their healthy peers. These results suggest that BMD measurement at initial evaluation may be necessary in this population.

Low TSH Levels Within Euthyroid Range Could Play a Negative Role on Bone Mineral Density in Postmenopausal Women with Type 2 Diabetes

OBJECTIVE

We aimed to evaluate the relationship between thyroid-stimulating hormone (TSH) and bone mineral density (BMD) in euthyroid type 2 diabetes (T2D).

METHODS

This retrospective analysis enrolled 439 T2D patients with normal thyroid function, including 226 males and 213 females. All the female patients were postmenopausal. Serum glycosylated hemoglobin A1c (HbA1c), TSH, free triiodothyronine (FT₃), and free thyroxine (FT₄) concentrations were analyzed. BMD of the lumbar spine (L₁-L₄), femoral neck, and hip joint was determined using dual-energy X-ray absorptiometry.

RESULTS

The patients were grouped based on tri-sectional quantiles of the TSH levels: 0.55~1.70mIU/L (Group 1), 1.71~2.58mIU/L (Group 2), and 2.59~4.74mIU/L (Group 3). Our data showed that, in male patients, no difference in BMD was identified among groups. In postmenopausal women, unlike at the lumbar spine (P = 0.459), the mean BMD at the femoral neck (P = 0.014) and hip joint (P = 0.014) had a statistical difference among groups and increased with TSH level. In addition, our analysis demonstrated that TSH levels shown no correlation with BMD at all sites in males. However, in females, BMD at the femoral neck (r = 0.156, P = 0.023) and hip joint (r = 0.172, P = 0.012) had a positive correlation with TSH levels. After adjusting for age and BMI, multiple regression analysis showed that TSH levels influenced BMD at the femoral neck (β = 0.188, P = 0.001) and hip joint (β = 0.204, P = 0.001) in female patients.

CONCLUSION

In summary, our data demonstrates that low TSH levels are associated with decreased BMD at the femoral neck and hip joint in postmenopausal T2D women with euthyroidism.

The Influence of Thyroid Pathology on Osteoporosis and Fracture Risk: A Review

Thyroid hormones are important factors that regulate metabolism and cell differentiation throughout the human body. A complication of thyroid pathology is represented by an alteration of the bone metabolism which can lead to osteoporosis and fragility fractures, known to have a high mortality rate. Although there is a consensus on the negative impact of hyperthyroidism on bone metabolism, when referring to hypothyroidism, subclinical hypothyroidism, or subclinical hyperthyroidism, there is no general agreement. The aim of our review was to update clinicians and researchers about the current data regarding the bone health in hypothyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism patients. Thyroid disorders have an important impact on bone metabolism and fracture risk, such that hyperthyroidism, hypothyroidism, and subclinical hyperthyroidism are associated with a decreased bone mineral density (BMD) and increased risk of fracture. Subclinical hypothyroidism, on the other hand, is not associated with osteoporosis or fragility fractures, and subclinical hyperthyroidism treatment with radioiodine could improve bone health.

Subclinical thyroid dysfunction, bone mineral density, and osteoporosis in a middle-aged Korean population

Thyroid dysfunction is associated with the loss of bone density (osteoporosis). However, the connection between subclinical thyroid dysfunction and osteoporosis remains controversial. This study found no apparent association between subclinical hypothyroidism or subclinical hyperthyroidism and bone mineral density (BMD) in the lumbar spine and femur.

INTRODUCTION

The present study examined the relationship between subclinical thyroid dysfunction and BMD in healthy middle-aged adults.

METHODS

A total of 25,510 healthy Koreans with normal free thyroxine levels were enrolled from January 2011 to December 2016, and 91% of subjects visited only once. The average age of the 15,761 women was 45, and the average age of the 9749 men was 48. Levels of thyroid-stimulating hormone (TSH) and BMD were recorded in all subjects. BMD was measured using dual-energy X-ray absorptiometry.

RESULTS

No apparent association was found between subclinical thyroid dysfunction and BMD in the lumbar spine, femur-neck, and proximal femur sites compared with a euthyroid group. Age, body mass index (BMI), and postmenopausal status affected BMD in women, and only BMI affected BMD in men. Subclinical hypothyroidism was independently associated with a lower risk of osteoporosis (odds ratio 0.657, 95% confidence interval 0.464-0.930) in 4710 postmenopausal women.

CONCLUSIONS

No apparent association was found between subclinical hypothyroidism or subclinical hyperthyroidism defined on single TSH measurement and BMD at the lumbar spine and femur in a large cohort of middle-aged men and women. Subclinical hypothyroidism was independently associated with a lower risk of osteoporosis in postmenopausal women.

Evaluation of Thyroid Hormone Status and Bone Density Ratio in Euthyroid Postmenopausal Women in Early and Late Stage of Bone Loss

Introduction:

Osteoporosis is a consequence of reduction in bone mass and disorders of bone structure, which makes the bones prone to fractures. Physiological variations of thyroid-stimulating hormone (TSH) may be an early indicator of the predisposing basis of the emergence of osteoporosis.

Aim:

To evaluate the thyroid hormone status and bone density ratio in euthyroid postmenopausal women in early and late stage of bone loss.

Methods:

The research is an observational, intersected, controlled study involving postmenopausal women admitted to the Clinic for Nuclear medicine and endocrinology of the Clinical Center University of Sarajevo (CCUS). The study included a total of 120 postmenopausal subjects divided into two groups. First group included 60 postmenopausal patients with osteoporosis, 30 of them were at the early stage of postmenopause, and 30 were in the late postmenopausal phase. The second group consisted of 60 postmenopausal patients with preserved bone mass, 30 of which were in the early stage of postmenopause and 30 in the late postmenopausal phase. For all patients included in the study follicle-stimulating hormone (FSH), TSH, free thyroxine (FT4), free triiodothyronine (FT3) were analyzed.

Results:

The mean duration of the postmenopausal period was statistically significantly higher in the group of women with osteoporosis (11.4 ± 1.1 years). The mean values of FSH were statistically significantly higher in the group of women with osteoporosis (54.0 ± 2.6 IU / L). The mean level of TSH and FT3 did not statistically significantly differ in the group of women with osteoporosis compared to the control group of women. The mean FT4 level in women with osteoporosis was statistically significantly lower (14.7 ± 0.29 pmol / L) compared to the control group of women (15.95 ± 0.3 pmol / L) (p = 0.004).

Conclusion:

In our examined group, the FT4 patient (mean) was significantly lower in the serum of women with osteoporosis compared to subjects with preserved bone mass. It would be most effective to recognize risk factors in order to influence them on time, and to alleviate and slow down the consequences of osteoporosis. One of these possible factors is the hormonal status of the thyroid gland, that is, TSH whose physiological variations may be an early indicator of the predisposing basis for the emergence of osteoporosis. The frequency and prevalence of these medical problems require additional research, and it is also a great challenge to understand the effects of thyroid hormone on bone tissue.

Brain to bone: What is the contribution of the brain to skeletal homeostasis?

The brain, which governs most, if not all, physiological functions in the body, from the complexities of cognition, learning and memory, to the regulation of basal body temperature, heart rate and breathing, has long been known to affect skeletal health. In particular, the hypothalamus - located at the base of the brain in close proximity to the medial eminence, where the blood-brain-barrier is not as tight as in other regions of the brain but rather "leaky", due to fenestrated capillaries - is exposed to a variety of circulating body cues, such as nutrients (glucose, fatty acids, amino acids), and hormones (insulin, glucagon, leptin, adiponectin) [1-3].Information collected from the body via these peripheral cues is integrated by hypothalamic sensing neurons and glial cells [4-7], which express receptors for these nutrients and hormones, transforming these cues into physiological outputs. Interestingly, many of the same molecules, including leptin, adiponectin and insulin, regulate both energy and skeletal homeostasis. Moreover, they act on a common set of hypothalamic nuclei and their residing neurons, activating endocrine and neuronal systems, which ultimately fine-tune the body to new physiological states. This review will focus exclusively on the brain-to-bone pathway, highlighting the most important anatomical sites within the brain, which are known to affect bone, but not covering the input pathways and molecules informing the brain of the energy and bone metabolic status, covered elsewhere [8-10]. The discussion in each section will present side by side the metabolic and bone-related functions of hypothalamic nuclei, in an attempt to answer some of the long-standing questions of whether energy is affected by bone remodeling and homeostasis and vice versa.

Waist Circumference and Subclinical Thyroid Dysfunction in a Large Cohort of Chinese Men and Women

OBJECTIVE

The association between subclinical thyroid dysfunction and waist circumference (WC) is still controversial, especially from the perspective of sex differences. We aimed to explore the impact of sex on this relationship in a large Chinese cohort.

METHODS

This cross-sectional study recruited 13,505 healthy participants (8,346 males, 5,159 females) who were enrolled in a health check program. Clinical data were collected. The association between subclinical thyroid dysfunction and WC of both sexes was analyzed separately after dividing WC into quartiles. Odds ratios (ORs) were calculated by binary logistic regression models, and linear regression analysis was also performed.

RESULTS

The prevalence rates of subclinical hyper-and hypothyroidism were significantly lower in males. Binary logistic regression models showed that WC in females with subclinical hypothyroidism had a detrimental effect with an OR of 1.011, but the effect disappeared when we included other covariates. The other ORs indicated no significant effects. The weak negative relationship between WC and thyrotropin was also indicated by linear regression analyses with very low R² values.

CONCLUSION

The current research did not show WC as a risk factor for subclinical thyroid dysfunction in either sex. Regional and ancestral origin differences may account for the variations with other studies.

ABBREVIATIONS

ALT = alanine aminotransferase; BMI = body mass index; FT3 = free triiodothyronine; FT4 = free thyroxine; TG = triglycerides; TSH = thyroid-stimulating hormone; UA = uric acid; WC = waist circumference.

Pituitary Diseases and Bone

Neuroendocrinology of bone is a new area of research based on the evidence that pituitary hormones may directly modulate bone remodeling and metabolism. Skeletal fragility associated with high risk of fractures is a common complication of several pituitary diseases such as hypopituitarism, Cushing disease, acromegaly, and hyperprolactinemia. As in other forms of secondary osteoporosis, pituitary diseases generally affect bone quality more than bone quantity, and fractures may occur even in the presence of normal or low-normal bone mineral density as measured by dual-energy X-ray absorptiometry, making difficult the prediction of fractures in these clinical settings. Treatment of pituitary hormone excess and deficiency generally improves skeletal health, although some patients remain at high risk of fractures, and treatment with bone-active drugs may become mandatory. The aim of this review is to discuss the physiological, pathophysiological, and clinical insights of bone involvement in pituitary diseases.

Thyroid diseases and bone health

Thyroid hormones are essential for skeletal development and are important regulators of bone maintenance in adults. Childhood hypothyroidism causes delayed skeletal development, retarded linear growth and impaired bone mineral accrual. Epiphyseal dysgenesis is evidenced by classic features of stippled epiphyses on X-ray. In severe cases, post-natal growth arrest results in a complex skeletal dysplasia. Thyroid hormone replacement stimulates catch-up growth and bone maturation, but recovery may be incomplete dependent on the duration and severity of hypothyroidism prior to treatment. A severe phenotype characteristic of hypothyroidism occurs in children with resistance to thyroid hormone due to mutations affecting THRA encoding thyroid hormone receptor α (TRα). Discovery of this rare condition recapitulated animal studies demonstrating that TRα mediates thyroid hormone action in the skeleton. In adults, thyrotoxicosis is well known to cause severe osteoporosis and fracture, but cases are rare because of prompt diagnosis and treatment. Recent data, however, indicate that subclinical hyperthyroidism is associated with low bone mineral density (BMD) and an increased risk of fracture. Population studies have also shown that variation in thyroid status within the reference range in post-menopausal women is associated with altered BMD and fracture risk. Thus, thyroid status at the upper end of the euthyroid reference range is associated with low BMD and increased risk of osteoporotic fragility fracture. Overall, extensive data demonstrate that euthyroid status is required for normal post-natal growth and bone mineral accrual, and is fundamental for maintenance of adult bone structure and strength.

Pituitary-bone connection in skeletal regulation

Pituitary hormones have traditionally been thought to exert specific, but limited function on target tissues. More recently, the discovery of these hormones and their receptors in organs such as the skeleton suggests that pituitary hormones have more ubiquitous functions. Here, we discuss the interaction of growth hormone (GH), follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), prolactin, oxytocin and arginine vasopressin (AVP) with bone. The direct skeletal action of pituitary hormones therefore provides new insights and therapeutic opportunities for metabolic bone diseases, prominently osteoporosis.

Low Normal TSH levels are Associated with Impaired BMD and Hip Geometry in the Elderly

Subclinical hyperthyroidism is known to be associated with the risk of fractures in elderly people. However, there are few studies assessing whether low normal thyroid-stimulating hormone (TSH) levels affect bone density and geometry. Here, we aimed to assess the influence of the TSH level on bone mineral density (BMD) and geometry in elderly euthyroid subjects. This was a cross-sectional cohort study. A total of 343 men and 674 women with euthyroidism were included and analyzed separately. The subjects were divided into tertiles based on the serum TSH level. The BMD and geometry were measured using dual-energy X-ray absorptiometry and a hip structural analysis program. Multiple regression analysis was used to compute the odds ratios of osteoporosis in the lower TSH tertile group and the association between geometry parameters and the TSH level. We found that the femoral neck and total hip BMDs were lower in the lower TSH tertile group. In women, the cross-sectional area and cortical thickness of the femur were negatively associated with the TSH level in all three regions (the narrow neck, intertrochanter, and femoral shaft); however, in men, these geometry parameters were significantly associated with the TSH level only in the intertrochanter region. The buckling ratio, a bone geometry parameter representing cortical instability, was significantly higher in the lower TSH tertile group in all three regions in women, but not in men. Our results indicated that lower TSH levels in the euthyroid range are related to lower BMD and weaker femoral structure in elderly women.

Lessons from the Bone Chapter of the Malaysian Aging Men Study

Male osteoporosis in Malaysia is a largely neglected problem. Therefore, a bone health study in men using quantitative ultrasonometry was launched as part of the Malaysian Aging Men Study in 2009–2012. This review aimed to summarize the findings of the aforementioned bone health study. The study examined the bone health of Chinese and Malaysian men aged 20 years and above living in Kuala Lumpur using a quantitative ultrasound device. Participants answered a questionnaire on their demographic details and physical activity status. Body anthropometry of the participants was measured and their blood collected for biochemical analysis. Results showed that a significant proportion of the Malaysian Chinese and Malay men had suboptimal bone health indicated by calcaneal speed of sound and vitamin D status. Age-related decline of the calcaneal speed of sound in these men was gradual and biphasic without ethnic difference. Body anthropometry such as height, weight, body mass index, and body fat percentage contributed to the variation of the calcaneal speed of sound in Malaysian men. Age-related changes in testosterone, insulin-like growth factor 1, and thyroid stimulating hormone also influenced the calcaneal speed of sound in these men. This study serves as a reminder that male osteoporosis in Malaysia should be an issue of concern. It is also a basis for a more comprehensive study on bone health in men in the future.

Evaluation of thyroid function status among postmenopausal women with and without osteoporosis

OBJECTIVE

To investigate the relationship between thyroid function status and bone mineral density (BMD) among women with postmenopausal osteoporosis.

METHODS

A retrospective study was performed among 1217 women aged 45-80years who attended the Department of Obstetrics and Gynecology at Dokuz Eylul University, Izmir, Turkey, between August 1, 2009, and June 1, 2013. Eligible participants were grouped according to the presence or absence of osteoporosis as defined by BMD measurements at the lumbar vertebrae (L1-L4), femoral neck, or trochanter of the femur. Serum levels of free tri-iodothyronine, free tetraiodothyronine, and thyroid-stimulating hormone (TSH) were assessed.

RESULTS

The 303 women with osteoporosis had a lower mean TSH level (1.8mIU/L) than did the 914 women without osteoporosis (1.9mIU/L; P=0.01). A positive correlation between TSH level and measures of BMD was observed (P=0.01). The TSH level was associated with a protective effect in a regression model for development of osteoporosis; the odds ratio was 0.68 (95% confidence interval 0.53-0.86).

CONCLUSION

Osteoporosis appeared to be independently associated with serum TSH level. Maintaining TSH levels within the upper limit of the reference range during treatment of hypothyroidism could be important to prevent osteoporosis among postmenopausal women.

Role of Thyroid Hormones in Skeletal Development and Bone Maintenance

The skeleton is an exquisitely sensitive and archetypal T3-target tissue that demonstrates the critical role for thyroid hormones during development, linear growth, and adult bone turnover and maintenance. Thyrotoxicosis is an established cause of secondary osteoporosis, and abnormal thyroid hormone signaling has recently been identified as a novel risk factor for osteoarthritis. Skeletal phenotypes in genetically modified mice have faithfully reproduced genetic disorders in humans, revealing the complex physiological relationship between centrally regulated thyroid status and the peripheral actions of thyroid hormones. Studies in mutant mice also established the paradigm that T3 exerts anabolic actions during growth and catabolic effects on adult bone. Thus, the skeleton represents an ideal physiological system in which to characterize thyroid hormone transport, metabolism, and action during development and adulthood and in response to injury. Future analysis of T3 action in individual skeletal cell lineages will provide new insights into cell-specific molecular mechanisms and may ultimately identify novel therapeutic targets for chronic degenerative diseases such as osteoporosis and osteoarthritis. This review provides a comprehensive analysis of the current state of the art.

Occurrence of osteoporosis & factors determining bone mineral loss in young adults with Graves' disease

Background & objectives:

There is a paucity of data with conflicting reports regarding the extent and pattern of bone mineral (BM) loss in Graves’ disease (GD), especially in young adults. Also, interpretation of BM data in Indians is limited by use of T-score cut-offs derived from Caucasians. This study was aimed to evaluate the occurrence of osteoporosis in active treatment naive patients with GD and determine the factors predicting BM loss, using standard T-scores from Caucasians and compare with the cut-offs proposed by the Indian Council of Medical Research (ICMR) for diagnosing osteoporosis in Indians.

Methods:

Patients with GD, >20 yr age without any history of use of anti-thyroid drugs, and normal controls without fracture history, drugs use or co-morbidities underwent BM density (BMD) assessment at lumbar spine, hip and forearm, thyroid function and calcium profile assessment. Women with menopause or premature ovarian insufficiency and men with androgen deficiency were excluded.

Results:

Patients with GD (n=31) had significantly lower BMD at spine (1.01±0.10 vs. 1.13±0.16 g/cm²), hip (0.88±0.10 vs. 1.04±0.19 g/cm²) and forearm (0.46±0.04 vs. 0.59±0.09 g/cm²) compared with controls (n=30) (P<0.001). Nine (29%) and six (19.3%) patients with GD had osteoporosis as per T-score and ICMR criteria, respectively. None of GD patients had osteoporosis at hip or spine as per ICMR criteria. Serum T₃ had strongest inverse correlation with BMD at spine, hip and femur. Step-wise linear regression analysis after adjusting for age, BMI and vitamin D showed T₃ to be the best predictor of reduced BMD at spine, hip and forearm, followed by phosphate at forearm and 48 h I¹³¹ uptake for spine BMD in GD.

Interpretation & conclusions:

Osteoporosis at hip or spine is not a major problem in GD and more commonly involves forearm. Diagnostic criterion developed from Caucasians tends to overdiagnose osteoporosis in Indians. T₃ elevation and phosphate are important predictors of BMD. Baseline I¹³¹ uptake may have some role in predicting BMD.

High-normal free thyroxine levels are associated with low trabecular bone scores in euthyroid postmenopausal women

Trabecular bone scores (TBS) have recently been developed as a diagnostic tool to assess bone texture. We studied thyroid status and TBS in a population-based cohort and demonstrated that high-normal thyroxine levels are associated with low TBS in healthy euthyroid postmenopausal women.

INTRODUCTION

Increased thyroid hormone levels affect bone mineral density (BMD) and, if untreated, increase the risk of fracture. However, the relationship between thyroid function and bone microarchitecture has not yet been established. Trabecular bone scores (TBS) are gray-level textural measurements of dual energy X-ray absorptiometry (DXA) images. The TBS has been proposed as an indirect index of bone microarchitecture. The goal of this study was to characterize the relationship between thyroid function and TBS in euthyroid men and postmenopausal euthyroid women.

METHODS

A total of 1376 euthyroid subjects (648 postmenopausal women and 728 men) were recruited from a community-based cohort in Korea. Free thyroxine (fT4) levels, thyroid stimulating hormone (TSH) levels, BMD, and TBS were measured and compared.

RESULTS

There was no significant relationship between either fT4 or TSH levels and BMD in men and women. Multiple linear regression analysis showed that high-normal fT4 levels were negatively correlated with TBS (β = -0.111; P = 0.002, after adjusting for both age and body mass index [BMI]) in postmenopausal women. In men, however, there was no significant correlation between fT4 levels and TBS. TSH levels were not significantly associated with TBS in either men or women.

CONCLUSION

Higher fT4 levels within the normal reference range are associated with deterioration of trabecular microarchitecture in healthy euthyroid postmenopausal women.

Risk Factors of Bone Mass Loss at the Lumbar Spine: A Longitudinal Study in Healthy Korean Pre- and Perimenopausal Women Older than 40 Years

Longitudinal studies on bone mass decline for healthy women are sparse. We performed a retrospective longitudinal study to evaluate the factor associated with bone mass changes at the lumbar spine in healthy Korean pre- and perimenopausal women over the age of 40. We examined the relation of blood tests including thyroid function tests at baseline and follow-up to the annual percentage changes in average BMD of L2-L4 (A%ΔLSBMD). Four hundred and forty-three subjects without diseases or medications pertaining to bone metabolism were analyzed. The mean A%ΔLSBMD in these subjects was -0.45%/year. Though a significant correlation was observed between the A%ΔLSBMD and age, serum thyroid-stimulating hormone (TSH) level, total cholesterol (TC) level, low-density lipoprotein cholesterol (LDL-C) level, and estimated glomerular filtration rate (eGFR) at baseline and follow-up, there was a weak correlation between A%ΔLSBMD and these variables. From multiple linear regression analyses, the percent body fat, age, serum TSH level, serum uric acid level, and the menopause at follow-up were showed to have a significant association with the A%ΔLSBMD. Unlike age, percent body fat, and menopause at follow-up, which had a negative association with the A%ΔLSBMD, serum TSH level and serum uric acid level, had a positive association with the A%ΔLSBMD. The results from our study showed that the notable risk factors of BMD loss at the lumbar spine in population of our study were advancing age, menopause, higher percent body fat, lower normal TSH, and lower serum uric acid levels.

A cross-sectional study to examine the correlation between serum TSH levels and the osteoporosis of the lumbar spine in healthy women with normal thyroid function

We examined the association between serum TSH levels and osteoporosis of the lumbar spine in 756 Korean women aged 65 years or older with normal thyroid function. Low-normal serum TSH levels might be a potential risk factor for the osteoporosis in non-obese elderly women.

INTRODUCTION

We aimed to examine the association between serum thyroid-stimulating hormone (TSH) levels and osteoporosis of the lumbar spine in healthy elderly Korean women with normal thyroid function.

METHODS

In this cross-sectional study, we evaluated the correlations between serum TSH levels and the osteoporosis of the lumbar spine depending on the body mass index (BMI) in a total of 756 women aged 65 years or older who underwent bone mineral density (BMD) measurement and thyroid function test in a routine health screening examination at our medical institution.

RESULTS

After the adjustment of the age and BMI, there was a significant positive correlation between serum TSH level within normal range and the BMD of the lumbar spine (r = 0.165, P < 0.001). In the non-obese elderly women, multivariate-adjusted odds ratios (ORs) for the osteoporosis of the lumbar spine were significantly higher in the 1st and 2nd quartiles of serum TSH levels as compared with their 4th quartile (OR 2.169, 95% CI 1.128-4.171; and OR 2.122, 95% CI 1.123-4.007, respectively). In these women, there were dose-dependent inverse correlations between quartiles of serum TSH levels and the osteoporosis of the lumbar spine (P for trend, 0.008). In the obese women, however, there were no such correlations.

CONCLUSIONS

In conclusion, our results suggest that low-normal serum TSH levels might be a potential risk factor for the osteoporosis of the lumbar spine in non-obese elderly women. But further prospective, large-scale, randomized controlled studies are warranted to establish our results.

Hypothalamic control of bone metabolism

Bones are structures in vertebrates that provide support to organs, protect soft organs, and give them shape and defined features, functions that are essential for their survival. To perform these functions, bones are constantly renewed throughout life. The process through which bones are renewed is known as bone remodeling, an energy demanding process sensitive to changes in energy homeostasis of the organism. A close interplay takes place between the diversity of nutritional cues and metabolic signals with different elements of the hypothalamic circuits to co-ordinate energy metabolism with the regulation of bone mass. In this review, we focus on how mouse and human genetics have elucidated the roles of hormonal signals and neural circuits that originate in, or impinge on, the hypothalamus in the regulation of bone mass. This will help to understand the mechanisms whereby regulation of bone is gated and dynamically regulated by the hypothalamus.

Low serum thyrotropin level and duration of suppression as a predictor of major osteoporotic fractures-the OPENTHYRO register cohort

The relationship between thyrotoxicosis and osteoporotic fractures remains controversial, particularly in men. Register-based cohort study including all patients with a serum thyrotropin (TSH) measurement in the region of Funen 1996-2010. All TSH determinations were done in the same lab, which served all hospitals and General Practice (GP) practices in the region. Persons with raised TSH or a history of thyroid/pituitary disease or use of thyroid medications were excluded. The study population consisted of 222,138 (96%) persons with normal and 9217 (4%) with low TSH (<0.3 mIU/L). A single low TSH at baseline was associated with increased risk of hip fractures (adj HR 1.16, 95% CI 1.07-1.26, p < 0.001) but not major osteoporotic fractures (MOF, adj HR 1.06, 95% CI 0.99-1.12, p = 0.058) over a median follow-up of 7.5 years. When men were analyzed separately, results did not reach statistical significance. We found a significant association between duration of thyrotoxicosis and fracture. For each 6 months in which the mean TSH value was decreased (<0.3 mIU/L), hip fracture risk increased by a factor 1.07 (adj HR, 95% CI 1.04-1.10, p < 0.001) and MOF by 1.05 (adj HR, 95% CI 1.03-1.07, p < 0.001). Overt thyrotoxicosis was associated with an increased risk of hip fractures but not MOF. In euthyroid patients, the risk of fractures increased significantly with each SD unit of TSH decrease: Hip fracture (HR 1.45, 95% CI 1.22-1.71, p < 0.001) and MOF (HR 1.32, 95% CI 1.19-1.46, p < 0.001). In a population-based cohort, a single, first measurement of decreased TSH in patients without known thyroid disease was associated with an increased long-term risk of hip fracture, which remained significant in women but not in men after adjusting for confounders. Moreover, the risk of both hip fracture and MOF increased exponentially by the length of time during which TSH had remained low.

Subclinical thyroid dysfunction and hip fracture and bone mineral density in older adults: the cardiovascular health study

BACKGROUND

Subclinical thyroid dysfunction is common in the elderly, yet its relationship with hip fracture and bone mineral density (BMD) is unclear.

OBJECTIVE

We examined the association between endogenous subclinical hyper- and hypothyroidism and hip fracture and BMD in older adults.

METHODS

A total of 4936 US individuals 65 years old or older enrolled in the Cardiovascular Health Study and not taking thyroid preparations were included. Analyses of incident hip fracture were performed by thyroid status, over a median follow-up of 12 years. A cross-sectional analysis of thyroid status and BMD was performed in a subset of 1317 participants who had dual-energy x-ray absorptiometry scans. Models were adjusted for risk factors and stratified by sex.

RESULTS

No association was found between subclinical hypothyroidism and incident hip fracture compared with euthyroidism, when assessed at a single time point or persisting at two time points, in either women [hazard ratio (HR) 0.91, 95% confidence interval (CI) 0.69-1.20 for a single and HR 0.79, 95% CI 0.52-1.21 for two time points] or men (HR 1.27, 95% CI 0.82-1.95 for a single and HR 1.09, 95% CI 0.57-2.10 for two time points). Likewise, no association was found between subclinical hyperthyroidism and incident hip fracture in either sex (HR 1.11, 95% CI 0.55-2.25 in women and HR 1.78, 95% CI 0.56-5.66 in men). No association was found between subclinical thyroid dysfunction and BMD at the lumbar spine, total hip, or femoral neck sites.

CONCLUSIONS

Our data suggest no association between subclinical hypothyroidism or subclinical hyperthyroidism and hip fracture risk or BMD in older men and women. Additional data are needed to improve the precision of estimates for subclinical hyperthyroidism and in men.

Association between a serum thyroid-stimulating hormone concentration within the normal range and indices of obesity in Japanese men and women

OBJECTIVE

This cross-sectional study investigated the associations between the serum thyroid-stimulating hormone (TSH) concentration and indices of obesity in middle-aged Japanese men and women.

METHODS

The participants were 2,037 employees (1,044 men and 993 women; age, 36-55 yr) of a metal products factory in Japan. Clinical examinations were conducted in 2009. We obtained a medical history and anthropometric measurements (body weight, body mass index [BMI] and waist circumference) and measured the serum TSH concentrations. The anthropometric indices were compared across serum TSH quartiles. The associations were evaluated separately according to the smoking status in men.

RESULTS

The mean body weight (kg), BMI (kg/m(2)) and waist circumference (cm) were 69.2, 23.7 and 83.2 in men and 55.3, 22.3 and 74.3 in women, respectively. Men with a higher TSH concentration had higher body weight and BMI values (p for trend=0.016 and 0.019, respectively), and these significant associations were observed even after adjusting for age, smoking status and other potential confounders. The TSH level was not associated with waist circumference. We found a significant interaction between the TSH level and the smoking status on body weight (p for interaction=0.013) and a significant association between the TSH level and body weight in nonsmokers, but not in current smokers. No significant associations were observed between the TSH level and the anthropometric indices in women.

CONCLUSION

Significant positive associations between the serum TSH concentration, body weight and BMI were detected in men only, and an interaction with the smoking status was observed for this association.

Does thyroid function influence fracture risk? Prospective data from the HUNT2 study, Norway

OBJECTIVE

To prospectively study the relation between TSH and risk of hip and forearm fractures.

DESIGN

A population-based cohort study.

METHODS

In a substudy of the second survey of the Nord Trøndelag Health Study, Norway (HUNT2, 1995-97), linked with a hospital-based fracture registry, we investigated the relation between baseline TSH and risk of hip and/or forearm fractures.

POPULATION

A total of 16 610 women and 8595 men aged 40 years or more, without previous self-reported thyroid disease and hip or forearm fractures.

RESULTS

During 12.5 years follow-up, a total of 1870 women and 342 men experienced hip or forearm fractures. Overall, there was no relation between baseline TSH and fracture risk. However, there was weak evidence that women with TSH <0.5 and >3.5 mU/l had a slightly increased risk of hip fractures (hazard ratio (HR) 1.30, 95% CI 0.97-1.94 and HR 1.19, 95% CI 0.93-1.52) compared with the reference group with TSH of 1.5-2.4 mU/l. Supplementary analyses showed higher hip fracture risk in women with TSH >4.0 mU/l and negative thyroid peroxidase antibodies (TPOAb) compared with the reference group (HR 1.75, 95% CI 1.24-2.46).

CONCLUSION

We found no statistically significant relation between baseline TSH and subsequent fracture risk, but the data suggest a weak positive association with hip fracture risk among women with both low and high TSH. The latter association was confined to women with negative TPOAb status.

Thyroid-stimulating hormone is significantly associated with bone health status in men

BACKGROUND AND AIM

Recent studies revealed a novel association between thyroid-stimulating hormone (TSH) and bone health status in healthy male populations. The present study aimed to validate this association and provide new information on the relationship between TSH levels and calcaneal speed of sound (SOS) in men.

METHODS

This cross-sectional study recruited 681 men with complete data of calcaneal SOS, body anthropometry, serum TSH, free triiodothyronine (FT3) and free thyroxine (FT4) levels.

RESULTS

All subjects had FT3 and FT4 levels within the in-house reference range and 13 subjects had lower than normal TSH levels. The results revealed that the SOS value of subjects was significantly associated with TSH after multiple adjustments (p<0.05). When subjects were divided into quintiles according to their TSH levels, the difference of SOS between men with low-normal TSH and high-normal TSH contributed significantly to the association between TSH and bone health status (p<0.05). The significance of the association persisted with the inclusion and exclusion of subclinical hyperthyroid subjects.

CONCLUSIONS

There was a significant association between TSH levels and bone health status in men as assessed by quantitative ultrasound. This age-independent association between TSH and SOS might explain some of the individual variation of bone health status in men.

Subclinical hyperthyroidism and the risk of cardiovascular events and all-cause mortality: an updated meta-analysis of cohort studies

OBJECTIVES

Whether subclinical hyperthyroidism (SCH) results in poor prognosis remains controversial. Our aim was to evaluate the association between SCH and the risk of cardiovascular disease (CVD), cardiovascular mortality, and all-cause mortality by conducting a meta-analysis of cohort studies.

METHODS

The PubMed and Embase databases were searched through November 2011 to identify studies that met pre-stated inclusion criteria. Relevant information for analysis was extracted. Either a fixed or a random effects model was used to calculate the overall combined risk estimates.

RESULTS

Seventeen cohort studies were included in this meta-analysis. The overall combined relative risks for individuals with SCH compared with the reference group were 1.19 (95% confidence interval (CI): 1.10 to 1.28) for CVD, 1.52 (95% CI: 1.08 to 2.13) for cardiovascular mortality, and 1.25 (95% CI: 1.00 to 1.55) for all-cause mortality. Subgroup analysis by sample source (community or convenience sample) showed that the significant association for cardiovascular and all-cause mortality only existed when pooling studies from convenience samples. Heterogeneity was observed when pooling studies on the association between SCH and cardiovascular and all-cause mortality. Sensitivity analysis showed omission of each individual study did not significantly change the pooled effects. No evidence of publication bias was observed.

CONCLUSIONS

Our findings demonstrated that SCH significantly increased the risk of CVD for the general population and the risk of cardiovascular and all-cause mortality for the individuals with other morbidities.

The skeletal consequences of thyrotoxicosis

Euthyroid status is essential for normal skeletal development and the maintenance of adult bone structure and strength. Established thyrotoxicosis has long been recognised as a cause of high bone turnover osteoporosis and fracture but more recent studies have suggested that subclinical hyperthyroidism and long-term suppressive doses of thyroxine (T4) may also result in decreased bone mineral density (BMD) and an increased risk of fragility fracture, particularly in postmenopausal women. Furthermore, large population studies of euthyroid individuals have demonstrated that a hypothalamic-pituitary-thyroid axis set point at the upper end of the normal reference range is associated with reduced BMD and increased fracture susceptibility. Despite these findings, the cellular and molecular mechanisms of thyroid hormone action in bone remain controversial and incompletely understood. In this review, we discuss the role of thyroid hormones in bone and the skeletal consequences of hyperthyroidism.

Association between thyroid hormone levels, the number of circulating osteoprogenitor cells, and bone mineral density in euthyroid postmenopausal women

In postmenopausal women, an association between reduced bone mineral density (BMD) and increased number of circulating osteoprogenitor cells (COPs) has been found. Although an increased thyroid function is associated with BMD, thyroid hormones stimulate osteoblast function in vitro. We investigated whether thyroid hormones within the reference range were correlated with the number of COPs and stimulate mineralization in vitro. The number of COPs, defined as CD34+/alkaline phosphatase (AP)+ or CD34+/osteocalcin (OCN)+ cells, was quantified by fluorescence-activated cell sorting (FACS) analysis in 150 euthyroid postmenopausal women. Participants underwent measurement of serum free thyroxine (FT4), thyroid-stimulating hormone levels, and femur BMD. CD34+ cells were isolated from healthy volunteers irrespective of AP or OCN expression, and the effect of triiodothyronine (0.5-10 pmol/L)) on their ability to form mineralized nodules in vitro was studied. The number of COPs was highest among women with high-normal FT4 levels (>1.09 ng/dL). The FT4 levels were correlated positively with circulating log-CD34+/AP+ (r = 0.32, P < .001) and log-CD34/OCN+ cells (r = 0.36, P < .001) and inversely with total femur BMD (r = -0.17, P = .036) but not with femoral neck BMD. In a multivariate analysis, the FT4 levels were positively correlated with the number of COPs, independent of age and BMD. The ability of CD34+ cells to form mineralized nodules increased after exposure from low up to high-normal triiodothyronine concentrations (P for trend = .003). Among euthyroid postmenopausal women, high-normal FT4 levels are correlated with an increased number of circulating immature osteoprogenitor cells and a very mild BMD reduction. Exposure of CD34+ cells to physiological triiodothyronine concentrations stimulates mineralization in vitro.

Should we treat mild subclinical/mild hyperthyroidism? Yes

Whether or not subclinical hyperthyroidism (SCH) should be treated, remains a matter of debate because there are no randomized clinical trials answering the question if treatment improves long-term health outcomes. Cross-sectional and longitudinal population-based sudies demonstrate clear associations between SCH and risk on atrial fibrillation and fractures; associations with cardiovascular and overall mortality and mental health are less consistent. Associations with adverse outcomes of cardiovascular and bone health are in all likelihood causally related to SCH in view of an observed dose-response relationship and the existence of a plausible biologic mechanism. Short-term intervention studies show improvement of surrogate outcome measurements. Against this background treatment of both endogenous and exogenous SCH is recommended when TSH is 0.1 mU/l or lower. At TSH values>0.1-<0.4 mU/l treatment should be considered in the presence of risk factors (age>65 years, post menopause, osteoporosis, cardiac disease).

Low-normal or high-normal thyrotropin target levels during treatment of hypothyroidism: a prospective, comparative study

BACKGROUND

Recent literature advocates the decrease of the upper limit of the normal thyrotropin (TSH) reference range. The objective of this study was to determine whether treated hypothyroid patients maintained within a low-normal TSH range (0.4-2.0 mIU/L) have better clinical outcomes than those maintained within a high-normal TSH range (2.0-4.0 mIU/L).

METHODS

The study was performed in a thyroid outpatient clinic of a tertiary hospital. This was a prospective, interventional study. Forty-two participants with newly diagnosed overt primary hypothyroidism were paired in two groups: group 1 (n=20), low-normal target TSH; group 2 (n = 22), high-normal target TSH. Levothyroxine was initiated, and dose was adjusted to achieve and sustain the target TSH value during the study period. After the target TSH was reached, participants were evaluated every 3 months for thyroid function, serum lipid profile, resting energy expenditure (REE), body composition, and bone mineral density, for 12 months.

RESULTS

Nineteen patients in group 1 and 16 in group 2 completed the study. In the whole-group analysis, total cholesterol (p = 0.01), low-density lipoprotein cholesterol (p = 0.004), and triglycerides (p < 0.001) decreased after treatment, whereas REE per kilogram of lean body mass (p = 0.001) and total fat body mass (p =0.02) increased. Group 1 patients had a significantly higher relative increase in REE (+7.1% ± 11.3% vs. +3.6% ± 15.1%, p = 0.02). There was no difference between the groups in the other variables.

CONCLUSIONS

Despite recent trends toward lowering the upper limit of normal TSH range, the results of this 12-month study provided no substantial clinical evidence to corroborate that treatment of primary hypothyroidism should aim at maintaining TSH levels in a low-normal range

The relationship between thyroid function and bone mineral density in euthyroid healthy subjects in Taiwan

INTRODUCTION

It has been reported that low normal circulating thyrotropin (TSH) levels correlate with lower bone mineral density (BMD) in the Korean postmenopausal female. The goal of this study is to evaluate this relationship in different sex and age groups in a Chinese population.

MATERIALS AND METHODS

A total of 2,957 subjects in Taiwan, 1,343 males and 1,614 females, aged from 45 to 64 years, were enrolled in this study. They were divided into four groups: group 1 was males aged between 45 and 50 years (young male, YM); group 2 was females aged between 45 and 50 years (young female, YF); group 3 was males older than 50 years (old male, OM); and group 4 was females older than 50 years (old female, OF). Plasma total thyroxine (T4) and TSH were measured. BMD was quantified at the wrist using dual energy X-ray absorptiometry.

RESULTS

YM had the highest BMD whereas OF had the lowest BMD. Among the four groups, no significant correlation between TSH level and BMD was found in the four groups, but a significant negative correlation existed between T4 and BMD in OF (r = -0.089, p = 0.005) and YM (r = -0.109, p = 0.018).

CONCLUSION

Our study did not find significant correlations between TSH and BMD in both men and women with normal thyroid function in Taiwan. Weak negative correlations existed between T4 and BMD in postmenopausal women and young men. Further studies with measurement of FT4 and TSH and with a longitudinal design may shed light on this population difference.

The association between serum thyrotropin (TSH) levels and bone mineral density in healthy euthyroid men

OBJECTIVE

Although osteoporosis is increasingly shown to occur in a considerable proportion of men, data on risk factors for male osteoporosis are limited. In this study, we investigated the association between serum thyrotropin (TSH) concentration and bone mineral density (BMD) in healthy euthyroid men. Design A cross-sectional community (health promotion centre)-based survey.

SUBJECTS AND MEASUREMENTS

For 1478 apparently healthy euthyroid men who participated in a routine health screening examination, we measured BMD at the lumbar spine and femoral neck using dual energy X-ray absorptiometry and serum TSH concentrations using immunoluminometry.

RESULTS

Lumbar spine BMD linearly increased with TSH level after adjustment for age, weight and height (P for trend = 0.002), and statistical significance persisted after additional adjustment for smoking and drinking habits (P for trend = 0.010). When serum alkaline phosphatase was added as a confounding variable, the relationship was still significant (P for trend = 0.016). Femoral neck BMD also tended to increase in higher TSH concentration after adjustment for age, weight and height (P for trend = 0.042), but this association disappeared after additional adjustment for smoking and drinking habits. The odds of lower BMD (i.e. osteopaenia and osteoporosis combined) were significantly increased in subjects with low-normal TSH (i.e. 0.4-1.2 mU/l), when compared to high-normal TSH (i.e. 3.1-5.0 mU/l), after adjustment for confounding factors (odds ratio = 1.45, 95% CI = 1.02-2.10).

CONCLUSION

These results suggest that a serum TSH concentration at the lower end of the reference range may be associated with low BMD in men.

Thyroid function within the upper normal range is associated with reduced bone mineral density and an increased risk of nonvertebral fractures in healthy euthyroid postmenopausal women

CONTEXT

The relationship between thyroid function and bone mineral density (BMD) is controversial. Existing studies are conflicting and confounded by differences in study design, small patient numbers, and sparse prospective data.

OBJECTIVE

We hypothesized that variation across the normal range of thyroid status in healthy postmenopausal women is associated with differences in BMD and fracture susceptibility.

DESIGN

The Osteoporosis and Ultrasound Study (OPUS) is a 6-yr prospective study of fracture-related factors.

SETTING

We studied a population-based cohort from five European cities.

PARTICIPANTS

A total of 2374 postmenopausal women participated. Subjects with thyroid disease and nonthyroidal illness and those receiving drugs affecting thyroid status or bone metabolism were excluded, leaving a study population of 1278 healthy euthyroid postmenopausal women.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

We measured free T(4) (fT4) (picomoles/liter), free T(3) (fT3) (picomoles/liter), TSH (milliunits/liter), bone turnover markers, BMD, and vertebral, hip, and nonvertebral fractures.

RESULTS

Higher fT4 (beta = -0.091; P = 0.004) and fT3 (beta = -0.087; P = 0.005) were associated with lower BMD at the hip, and higher fT4 was associated with increasing bone loss at the hip (beta = -0.09; P = 0.015). After adjustment for age, body mass index, and BMD, the risk of nonvertebral fracture was increased by 20% (P = 0.002) and 33% (P = 0.006) in women with higher fT4 or fT3, respectively, whereas higher TSH was protective and the risk was reduced by 35% (P = 0.028). There were independent associations between fT3 and pulse rate (beta = 0.080; P = 0.006), increased grip strength (beta = 0.171; P<0.001), and better balance (beta = 0.099; P < 0.001), indicating that the relationship between thyroid status and fracture risk is complex.

CONCLUSIONS

Physiological variation in normal thyroid status is related to BMD and nonvertebral fracture.

The type 2 deiodinase Thr92Ala polymorphism is associated with increased bone turnover and decreased femoral neck bone mineral density

The role of type 2 deiodinase (D2) in the human skeleton remains unclear. The D2 polymorphism Thr92Ala has been associated with lower enzymatic activity, which could result in lower local triiodothyronine (T(3)) availability in bone. We therefore hypothesized that the D2 Thr92Ala polymorphism may influence bone mineral density (BMD) and bone turnover. We studied 154 patients (29 men, 125 women: 79 estrogen-replete, 46 estrogen-deficient) with cured differentiated thyroid carcinoma. BMD and bone turnover markers [bone-specific alkaline phosphatase (BAP), cross-linking terminal C-telopeptide of type I collagen (CTX), procollagen type 1 amino-terminal propeptide (P1NP), and cross-linked N-telopeptide of type I collagen (NTX)] were measured. Effects of the D2 Thr92Ala polymorphism on BMD and bone turnover markers were assessed by a linear regression model, with age, gender, estrogen state, body mass index (BMI), serum calcium, 25-hydroxyvitamin D, parathyroid hormone (PTH), thyroid-stimulating hormone (TSH), and free triiodothyroxine (T(4)) as covariables. Sixty patients were wild type (Thr/Thr), 66 were heterozygous (Thr/Ala), and 28 were homozygous (Ala/Ala) for the D2 polymorphism. There were no significant differences in any covariables between the three genotypes. Subjects carrying the D2 Thr92Ala polymorphism had consistently lower femoral neck and total hip densities than wild-type subjects (p = .028), and this was accompanied by significantly higher serum P1NP and CTX and urinary NTX/creatinine levels. We conclude that in patients with cured differentiated thyroid carcinoma, the D2 Thr92Ala polymorphism is associated with a decreased femoral neck BMD and higher bone turnover independent of serum thyroid hormone levels, which points to a potential functional role for D2 in bone.

Subclinical hypothyroidism and subclinical hyperthyroidism

Subclinical thyroid dysfunction occurs when peripheral thyroid hormone levels are within the normal laboratory reference range and the serum thyroid-stimulating hormone (TSH or thyrotropin) level is greater than normal (subclinical hypothyroidism) or less than normal (subclinical hyperthyroidism; TSH normal laboratory reference range: 0.3-5.0 mIU/l). For patients with subclinical hypothyroidism (serum TSH levels >10 mIU/l), thyroxine therapy is prescribed if other causes of TSH elevation and transient conditions have been excluded. For serum TSH levels between 5.0 and 10.0 mIU/l, selective therapy should be considered. For patients with sustained subclinical hyperthyroidism (serum TSH levels <0.1 mIU/l), therapy is recommended, especially in older patients. Observation or selective therapy should be considered for patients with serum TSH levels between 0.1 and 0.3 mIU/l.

Serum TSH values and risk of vertebral fractures in euthyroid post-menopausal women with low bone mineral density

INTRODUCTION

There is evidence that variations of thyrotropin (TSH) even in its reference range may influence bone mineral density (BMD). In fact, low-normal TSH values have been associated with high prevalence of osteoporosis in post-menopausal women. However, data associating TSH and risk of fractures are scanty and limited to subjects with subclinical thyrotoxicosis.

MATERIALS AND METHODS

In this observational study, we investigated the correlation between serum TSH and prevalence of radiological vertebral fractures in a cohort of 130 post-menopausal women with normal thyroid function.

RESULTS

Osteoporosis was observed in 80 women (61.5%), whereas 49 women (37.7%) had osteopenia. Vertebral fractures were found in 49 women (37.7%), who were significantly older, with higher prevalence of osteoporosis and with lower serum TSH values as compared with women who did not fracture. Stratifying the patients according to serum TSH values, vertebral fractures were found to be significantly (p=0.004) more prevalent in first tertile (56.8%) of TSH values as compared with the second (23.3%) and third tertiles (32.6%). Multivariate logistic regression analysis demonstrated that low serum TSH maintained a significant correlation with vertebral fractures (odds ratio 2.8, C.I. 95% 1.20-6.79) even after correction for age, BMD, BMI and serum free-thyroxine values.

DISCUSSION

Low-normal TSH values are associated with high prevalence of vertebral fractures in women with post-menopausal osteoporosis or osteopenia, independently of thyroid hormones, age and BMD.